The present invention relates to a toner for developing electrostatically charged images, which can provide excellent damage resistance to the formed images, a production method of the same, and an image forming method.
Employed as the quality performance standards of fixed images id xe2x80x9cfixed strengthxe2x80x9d as well as xe2x80x9cfixabilityxe2x80x9d. In such evaluation, noted are the adhesion force of fixed images on the image support (for example, recording paper), the destruction of fixed images, and the transference of destroyed materials to the fixing member and the like.
In recent years, higher image quality in printers and the like has been demanded. As a result, the presence and absence of damage on the surface of fixed images, especially photographic images, have become an important standard to evaluate said images.
For example, the quality of photographic images (black-and-white images as well as full color images) is markedly deteriorated due to the presence of abrasion caused by friction between recording papers, and scratches as well as dents caused by nails, stationery, and the like. Subsequently, demanded has been development of a technique for forming excellent damage resistant fixed images which are barely subjected to surface damage.
In view of the foregoing, the present invention has been achieved.
An object of the present invention is to provide a toner for developing electrostatically charged images, which can provide excellent damage resistance (that is, abrasion resistance, scratch resistance, and dent resistance).
Another object of the present invention is to provide a toner producing method which can form excellent damage resistant fixed images.
Still another object of the present invention is to provide an image forming method which can form excellent damage resistant fixed images.
It has been discovered that by utilizing a toner which comprises crystalline compounds having a specified chemical structure in an specified amount and exhibits specific thermal behavior during melting of crystals as well as during crystallization, it is possible to form high quality fixed images having the desired damage resistance.
The electrostatically charged image developing toner of the present invention comprises at least a binder resin and a colorant; also comprises crystalline compounds (hereinafter referred occasionally to as xe2x80x9cspecified crystalline compoundsxe2x80x9d) represented by General Formula (1) in an amount of 3 to 40 parts by weight per 100 parts by weight of said binder resins; and exhibits at least one recrystallization peak during the second heating process in the DSC (hereinafter referred to as DSC) curve of said toner, which is determined by employing a DSC.
One of the preferred examples of the electrostatically charged image developing toner of the present invention is comprised of particles which are obtained by direct polymerization of a monomer composition comprising said specified crystalline compounds and polymerizable monomers in a water phase.
Further, another example of said toner is comprised of particles which are obtained by coalescing fine particles obtained by directly polymerizing a monomer composition comprising said specified crystalline compounds and polymerizable monomers in a water phase.
In a production method of an electrostatically charged image developing toner in which at least a binder resin, a colorant, and a crystalline compound, represented by General Formula (1) are dry mixed, melt kneaded employing a kneader, pulverized, and if desired, classified, the toner production method of the present invention comprises a process which exhibits the maximum temperature during melt kneading which is higher than melting peak temperature t1m (in xc2x0 C.) of said crystalline compounds during the first heating process determined by a DSC and cools toner raw materials ejected from said kneader at a cooling rate of 1 to 20xc2x0 C./second to the specified temperature which is below (t1mxe2x88x9230xc2x0 C.).
Further, another toner production method of the present invention is an electrostatically charged image developing toner production method in which an electrostatically charged image developing toner, comprising at least a binder resin, a colorant, and a crystalline compound, represented by the general formula described below, is produced employing a polymerization method, and the maximum temperature during production is no less than melting peak temperature t1m (in xc2x0 C.) of said crystalline compound during the first heating process which is determined employing a DSC, and which comprises a process which cools toner raw materials from said maximum temperature to not more than (t1mxe2x88x9230xc2x0 C.) at a cooling rate of 1 to 20xc2x0 C./minute.
The image forming method of the present invention is one which comprises processes in which an electrostatically charged image formed on an electrostatic image bearing body is developed employing a toner; a toner image formed on said electrostatic image bearing body is transferred onto an image support and the transferred toner image is heated and pressure fixed employing a heating roller, by which fixed images are obtained. Said toner comprises at least a binder resin, a colorant, and a specified crystalline compound, and said crystalline compound exhibits at least one recrystallization peak during the second heating process in the DSC curve of said specific crystalline compound, which is determined employing a DSC.
Furthermore, the image forming method of the present invention is one which comprises processes in which an electrostatically charged image formed on an electrostatic image bearing body is developed employing a toner; the resultant toner image formed on said electrostatic image bearing body is transferred onto an image support; and the transferred toner image is thermally pressure fixed employing a heating roller, by which fixed images are obtained. Said toner comprises at least a binder resin, a colorant, and a specified crystalline compound, and said crystalline compound exhibits at least one recrystallization peak during the second heating process in the DSC curve of said specified crystalline compound, which is determined employing a DSC. The surface temperature of said heating roll is the same as said recrystallization peak temperature trc or higher, and the surface temperature of said image support 3 seconds after passing the fixing nip roll is at least 90xc2x0 C. lower than the surface temperature of said heating roll.
General Formula (1):
R1xe2x80x94(OCOxe2x80x94R2)n 
wherein R1 represents a hydrocarbon group having from 1 to 80 carbon atoms, which may have a substituent, or a group represented by formula of (LK1xe2x80x94Xxe2x80x94LK2)mxe2x80x94, wherein LK1 and LK2 represent a hydrocarbon group, which may have a substituent, and LK1 and LK2 may be same or different, m is a natural number of 1 or more, X represents O or xe2x80x94OCxe2x80x94, R2 represents a hydrocarbon group having from 1 to 80 carbon atoms, which may have a substituent, and n represents an integer of 1 to 15.